High temperature fatigue crack growth of Haynes 230

The fatigue crack growth of the nickel-based superalloy Haynes 230 was investigated at room temperature and 900 °C using digital image correlation (DIC). As expected, the crack growth rates at high temperature were much faster than at room temperature. However, the crack closure levels, which were determined using digital image correlation analysis techniques, were found to be similar for the two cases studied. DIC strain fields and the corresponding plastic zone sizes were compared between the two cases. From these strain fields, the slip irreversibility, the difference between forward and reversed strains at the crack tip, was quantitatively measured. The high temperature case had an order of magnitude higher amount of slip irreversibility. Slip irreversibility measurements were determined to be an effective method to compare fatigue crack growth of cases with differing temperatures.